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Food allergy basics

How allergies work

Have you ever wondered what happens inside your body for you to develop allergies?

This short animation provides a simple explanation about how we develop allergies and also what happens in our body to cause symptoms of an allergic reaction.

What is a food allergy? 

A food allergy occurs when a person’s immune systems reacts to a food (usually a protein in the food) that is harmless for most people. When eaten, the immune system releases large amounts of chemicals that trigger symptoms that can affect a person’s breathing, heart, skin and gut.

Some food allergies can be severe, causing potentially life-threatening allergic reactions known as anaphylaxis.

Food allergy occurs in around 1 in 10 babies, 1 in 20 children and 1 in 50 adults.

Australian allergy prevalence data

The common allergy causing foods are peanut, tree nut, egg, milk (dairy), sesame, fish, crustacea, mollusc, soy, wheat and lupin. However, any food has the potential to cause an allergic reaction.

There is no cure for food allergy – therefore avoidance of the food is essential to prevent reactions.

Is a food intolerance the same as food allergy?

No. A food intolerance does not involve the immune system. It is the inability to digest a food which can cause discomfort and distress, but is not life-threatening.

Signs and symptoms of an allergic reaction to foods

ASCIA Action Plans provide information about when and how to give an adrenaline (epinephrine) injector (EpiPen® or Anapen®). It is the go-to guide on how to manage an allergic reaction and should always be kept with the adrenaline injector device.

ASCIA Action plans EpiPen  ASCIA Action plans Anapen ASCIA Action Plan for allergy

MILD to MODERATE allergic reaction

  • Swelling of lips, face, eyes
  • Hives or welts
  • Tingling mouth
  • Abdominal pain, vomiting

Allergic reaction - man's back Allergic reaction on baby

SEVERE allergic reaction (anaphylaxis)

Watch for ANY ONE of the following:

  • Difficult or noisy breathing
  • Swelling of tongue
  • Swelling/tightness in throat
  • Difficulty talking and/or hoarse voice
  • Wheeze or persistent cough
  • Persistent dizziness or collapse
  • Pale and floppy (young children)

Severe allergic in a man

Anaphylaxis usually occurs within minutes, up to 2 hours after exposure to the food. 

Mild to moderate signs may not always occur before anaphylaxis. 

This animation explains the signs and symptoms of an allergic reaction and what to do if someone has an allergic reaction.

Treating anaphylaxis

It is important to lay the person flat – do not let them stand or walk.  If breathing is difficult, allow them to sit with their back supported and with their legs outstretched, but they should not sit on a chair with their legs down, or stand.

NAS patient positioning for anaphylaxis

In pregnancy, lay the person on their left side or sit supported with their legs outstretched. Babies should be held on their side, not upright. 

NAS patient positioning for anaphylaxis

Where possible, transport the person to the ambulance on a stretcher, even if they appear to have recovered. Do not allow the person to stand or walk. 

NAS patient positioning for anaphylaxis

Prompt administration of adrenaline is the first-line treatment for anaphylaxis. Adrenaline injectors contain a single dose of adrenaline and have been designed so that anyone in the community can use them in an emergency.

How to administer an adrenaline injector



More information about anaphylaxis is available from:

ASCIA website:

Allergy & Anaphylaxis Australia website:


Content updated October 2021